Volatile organic compounds (VOC) in water and soil are routinely analyzed by headspace analysis. A sample of water or soil mixed with water partially fills a closed septum vial and is heated, driving dissolved volatile organics out of solution and into the vapor headspace and establishing an equilibrium between the sample and the vapor. A portion of this vapor is then extracted for analysis by, typically, a form of gas chromatography. Sufficient vapor is extracted from the headspace to purge connecting lines to the gas chromotagraph with a representative sample. Sampling vapor avoids the introduction of non-volatile or solid particles into the inlet of the gas chromatograph, which is not desirable.
Known in the art are field-portable gas chromatograph/mass spectrometers (GC/MS) engineered specifically for on-site VOC analysis. These self-contained devices typically comprise a vacuum system, analytical components and power components within one compact unit and are capable of acquiring and analyzing VOC samples in the field, thus eliminating the problems associated with conventional collecting, shipping, storing, and analyzing of samples. The ability of such portable devices to provide confirmatory test results immediately on site make them particularly useful for hazardous-waste site investigations, and emergency response situations.
Unfortunately, these portable GC/MS devices do not work well in headspace analysis. Their sample vacuum pumping systems are not powerful enough to extract vapors from a headspace. In order to make the portable devices suitable for headspace analysis, portable device manufacturers have developed auxiliary equipment. Such equipment generally operates to replace the headspace vapor with a VOC-free make up gas as the vapor is extracted by the sample pumping system. This additional equipment is complex in operation and expensive.
It is therefore a feature of the present invention to provide a compact portable, apparatus which facilitates the extraction of vapor from the headspace of a sample vial for accurate VOC analysis. An advantage of the invention is the provision of a relatively simple and inexpensive apparatus for facilitating vapor extraction.
A further advantage of the present invention is that it facilitates the extraction of the entire headspace from sample vial, thus increasing the sensitivity of the analysis.
Other aspects and advantages of the invention are set forth in part herein and in part will be obvious herefrom, or may be attained by means of instrumentalities and combinations pointed out in the appended claims.